1. Field of the Invention
The present invention relates to treatment of water, and more specifically to treatment of water using a stable formulation of polyhexamethylene biguanide (PHMB) and a liquid or solid zinc salt for the treatment and prevention algae in recirculated and stagnant water systems.
2. Brief Description of the Art
Polyhexamethylene biguanide (PHMB) is a known fast-acting and broad spectrum antimicrobial compound that is used in a variety of applications including eye and skin treatment compositions (U.S. Pat. Nos. 7,569,212; 7,560,421), cleaning compositions (U.S. Pat. Nos. 7,511,006; 7,501,027; 7,494,963), preservatives (U.S. Pat. No. 7,537,776), and as a treatment (sanitizer) for water systems (U.S. Pat. No. 6,710,017). PHMB is used as a sanitizer or preservative to kill bacteria (including methicillin-resistant Staphylococcus aureus (MRSA), Salmonella, Campylobacter, and E. coli) and viruses, and to control algae in a wide range of applications, including preserving wet wipes; controlling odor in textiles; preventing microbial contamination in wound irrigation and sterile dressings; disinfecting medical/dental utensil and trays, farm equipment, animal drinking water, and hard surfaces for food handling institutions and hospitals; and to deodorize vacuums and toilets. PHMB is used in antimicrobial hand washes and rubs and air filter treatments as an alternative to ozone. As a preservative, PHMB is used in cosmetics, personal care products, fabric softeners, contact lens solutions, hand washes, and the like. For pool and spa applications, PHMB is sold under the tradename BAQUACIL by Arch Chemicals, Inc. (Norwalk, CT).
Organic algaecides are often added apart from a sanitizer either as part of a system combined with sanitizer and/ or oxidizer to prevent algal contamination in swimming pools. The most effective algae preventative treatment is copper sulfate and/or chelated copper products.
However, PHMB reacts with copper to form an insoluble colored precipitate. Thus, copper products are incompatible with PHMB in both a formulated product and at levels used to prevent algae in swimming pools (e.g., 0-2 ppm). What is needed in the art is a composition of long-lasting algae preventative and PHMB that does not form precipitates, and is effective for preventing algal contamination in stagnant or recirculating water systems. The present invention is believed to be an answer to that need.